Figure 6.

Electron transport chain. Protons are pumped from the inner mitochondrial membrane into the intermitochondrial space to create a concentration gradient. Adenosine triphosphate (ATP) synthase: the flow of hydrogen ions down the concentration gradient through ATP synthase activates catalytic sites and joins inorganic phosphate to adenosine diphosphate (ADP), resulting in the production of ATP. Uncoupling protein: permits passive movement of hydrogen ions across the mitochondrial membrane down the transmembrane proton gradient. The energy potential of the proton gradient is not used to produce ATP and is instead dissipated as heat.

NADH = nicotinamide adenine dinucleotide; FADH = flavin adenine dinucleotide